LSI - Latent Semantic Indexing

Latent Semantic Indexing - LSI

I’m receiving more and more emails pitching SEO and using the latest SEO spammers’ catchphrase, Latent Semantic Indexing, or LSI for short. I say latest, but LSI has been a term that has been banded about  about since 2005, but the spammers seems to be touting latent semantic indexing, as though it was invented yesterday and they have the secret! I’m also receiving emails from readers of the blog asking what Latent Semantic Indexing is and how does LSI affects search engine positioning, so I thought I should take the time to address it.

What is LSI ?

LSI, in as plain English as I can muster, is the identification of synonyms and related words and terms to a specific keyword or keyphrase. To give you an example: If I was writing an article about Lou Reed, I would want to include keyterms in the article, such as Velvet Underground, Nico, Perfect Day, Loni Anderson and Walk on the wild side. Why? Because if a search engine uses latent semantic indexing in its algorithm, it would recognise that these key words and keyphrases are related to Lou Reed and would make the article more relevant for the search term, “Lou Reed”.

To give you another example of how LSI works; if I were writing an article about the Eiffel Tower, I would be sure to use keyterms such as Paris, Moulin Rouge and arc de triomphe, as these terms are semantically linked to the keyterm, “Eiffel Tower”.

How do you know which Keyterms are Semantically Linked?

Semantic linking is common sense really and up until recently, when planning an article and taking into account LSI, you simply targeted the terms that you knew were linked to the subject of your article. For example, if I was writing an article about Glasgow Rangers, I might include Ally McCoist, Ibrox, Celtic and The Teddy Bears, as I know they are semantically linked via Latent Semantic Indexing.

However, Google now give you a helping hand in finding terms that are semantically linked and in my opinion, more importantly, terms that are being searched regularly in relation to Glasgow Rangers.

If you type Glasgow Rangers into a Google search box, then scroll to the bottom of the page and Google tell you eight terms that are semantically related to Glasgow Rangers and that are searched regularly. Also, if you have a Google toolbar (and if not, why not?) type the term in there and you will see a list below the search box of the most common searches related to Glasgow Rangers, such as Glasgow Rangers Football Club, Glasgow Rangers shop, etc.

LSI is common sense; use secondary keyterms that the majority of the public would closely relate the keyterm that you are targeting. Most good SEOs have been using Latent Semantic indexing for years without even realising it, so don’t be overly impressed by spam emails suggesting that the spammer is giving you something different by offering LSI - I’ve been using it since 1998, long before anyone came up with the term, but I would give it a different title - WGC - WRITING GOOD CONTENT!

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